Role of sigma receptors in ethanol reinforcement

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Summary: The application proposes a career development plan for Dr. Valentina Sabino, a pharmacologically-trained post-doctoral fellow committed to a research career in ethanol addiction aimed towards understand its molecular basis. The applicant will be mentored by Dr. George Koob in behavioral neuroscience methods and animal models of alcoholism and co-mentored by Dr. Pietro Sanna in immunohistochemical and molecular techniques. The project, to be conducted at The Scripps Research Institute in the rich neuroscience community of San Diego, concerns sigma receptors, unique mammalian binding sites that modulate other neurotransmitter systems and which are richly expressed in limbic brain structures. Pharmacological studies indicate that sigma receptors modulate actions of cocaine and methamphetamine. Recently, sigma receptors also have been proposed to modulate motivating properties of ethanol, consistent with findings of sigma receptor polymorphisms in human alcoholism. Until very recently, however, the understanding of sigma receptor systems had been hampered by the unavailability of specific, subtype-selective ligands or of mutant mouse models that lack sigma receptor subtypes. Furthermore, the role of sigma receptors in voluntary intake or self-administration of ethanol are unknown. The present multipdisciplinary application uses behavioral, pharmacologic, and molecular techniques to determine the modulatory role of sigma receptorswith subtype specificity on ethanol reward and reinforcementin distinct models of excessive ethanol consumption. Two models of excess ethanol intake will be studied in Specific Aims 1 and 3 -- genetically selected alcohol-preferring rats and withdrawn outbred rats made dependent during chronic, intermittent exposure to ethanol vapor, emphasizing positive and negative reinforcing properties of ethanol, respectively. Ethanol self-administration will be pharmacologically modulated (in Specific Aim 1), through the administration of novel a receptor ligands, and molecularly (in Specific Aim 2), through the use of o-1 receptor KO mice. The impact of chronic exposure to ethanol and of innate preference for ethanol on o receptor protein expression in discrete limbic brain regions will be investigated in Specific Aim 3. Relevance: The project will define the physiologic and potential therapeutic relevance of an undercharacterized modulatory receptor system for alcohol abuse and dependence.